As known in the art, examples of a combustor that can heat heating water flowing through the inside of a heat exchanging pipe in a combustion chamber by using a burner may include a boiler and a water heater and etc. That is, the boiler that is used in a general home, a public building, or the like is used for heating a room and supplying a hot water and the water heater heats cold water up to a predetermined temperature within a short time to allow a user to conveniently use the hot water. Most of the combustors such as the boiler and the water heater are constituted by a system that uses oil or gas as fuel and combusts the oil or gas by means of a burner, heat water by using combustion heat generated in the course of the combustion, and supplies the heated water (hot water) to a user.
The combustors are equipped with a heat exchanger that absorbs combustion heat generated from the burner and various methods for improving heat transfer efficiency of the heat exchanger have been proposed.
In the related art, a method of increasing the heat transfer area of a heat exchanging pipe by forming a plurality of fins on the outer surface of a heat exchanging pipe has been generally used. However, the manufacturing method of the heat exchanging pipe is complicated and the manufacturing cost increases, while the effect of heat transfer area by the fins is not substantially increased.
FIG. 1 is a view showing a rectangular heat exchanger of which the manufacturing method is simpler than that of a fin type heat exchanger of the related art.
The heat exchanger has a configuration in which both ends of heat exchanging pipes 1 having a rectangular cross-section with the width larger than the height are fitted in fixing plates 2 and 3, and end plates 4 and 5 are fixed to the fixing plate, for example, by brazing, i.e., braze-welding. A heating water inlet 6 and a heating water outlet 7 are formed at the end plates 4 and 5, respectively. The heat exchanging pipes 1 are connected by pipe connectors 8, respectively, such that heat water flowing through the heat water inlet 6 is discharged through the heating water outlet 7 after passing through the heat exchanging pipes 1 and the pipe connectors 8. The heat exchanger has the advantage in that the manufacturing method is simpler than that of a fin type heat exchanger and the heat transfer area can be sufficiently ensured.
However, a combustion gas due to combustion in a burner of the heat exchanger flows through the spaces between the heat exchanging pipes 1 in the direction of an arrow, but the flow path of the combustion gas is relatively short, such that the heat of the combustion gas is not sufficiently transferred to the heat exchanging pipes 1. Further, since the gaps between the heat exchanging pipes 1 are usually 1 to 2 mm in home boilers, as the boiler is operated and the heating water flows into the heat exchanging pipes 1, the heat exchanging pipes 1 are expanded by pressure of the heating water and block the flow path of the combustion gas, such that the heat exchange efficiency is reduced.